1. Field of the Invention
The present invention relates to an exposure method and an exposure device, and in particular relates to an exposure method and an exposure device which perform exposure while relatively moving a substrate and a photomask.
2. Description of the Related Art
In a liquid crystal display panel, a pair of substrates are arranged opposing to each other at a predetermined gap, and liquid crystals are filled therebetween. On one of the substrates, constituents are stacked such as pixel electrodes which apply voltage to the liquid crystals, switching elements such as thin film transistors which drive the pixel electrodes, various lines such as gate bus lines and source bus lines, and an alignment layer which provides a pretilt angle to the liquid crystals. On the other substrate, constituents are stacked such as a black matrix, color filter layers having predetermined colors, common electrodes, and an alignment layer.
An alignment process for aligning the liquid crystals toward a predetermined direction is applied to the alignment layers arranged on the substrates. Conventionally, a rubbing process using a material such as a textile material is used as the alignment process. However, a photoalignment process has recently been used alternatively as the alignment process. The photoalignment process is a process that provides predetermined alignment characteristics on a surface of an alignment layer through a step to project light energy onto the surface of the alignment layer at a predetermined incident angle.
Constituents such as the switching element, the various lines, the black matrix, and the color filter layers are arranged using a photolithographic process. For example. The color filter layer is formed through a step to coat the substrate surface with a photoresist material having a predetermined color, a step to project light energy onto a predetermined pattern region on the photoresist material using a photomask, and a step to remove an unnecessary portion of the photoresist material (e.g. a portion onto which the light energy is not projected).
As prior art literatures relating to the present invention, Japanese Patent Application Unexamined Publications Nos. 2005-024649 and Hei 11-133429 are cited.
An exposure step to project light energy onto a predetermined region on a surface of a substrate is indispensable in manufacturing of liquid crystal display panels. If deviation in an exposure position and/or an exposure range occurs, conditions such as of alignment of liquid crystals and of lines arranged on the substrate may become different from the designed conditions, causing the substrate to fail to have designed alignment or characteristics. For example, if deviation in a position and/or a range of light energy projection occurs in the exposure step to provide the photoalignment process to the alignment layer, it becomes impossible to provide the designed pretilt angle to the liquid crystals.
In addition, when projecting light energy onto the surface to be irradiated of the substrate using a photomask, the accuracy regarding the position and/or the range of light energy projection is significantly influenced by the dimensional accuracy of a pattern of light shielding portions and light transmitting portions which are arranged on the photomask, thereby rendering the photomask to be expensive. Moreover, the size of photomasks has been increased along with recent upsizing of substrates, resulting in even more expensive photomasks.
Further, when a large photomask is used, problems tend to occur such as change in the sizes of light shielding portions and light transmitting portions and deviation in alignment with the substrate, due to factors such as deformation and thermal expansion. Countermeasures against the problems are performed for example by suppressing the change in the sizes by managing the temperatures of the substrate and the photomask and by improving the accuracy of the mechanism for alignment and the control thereof, but such countermeasures result in complicated processes and increased running costs. Hence, the present invention aims to provide an exposure method and an exposure device capable of performing accurate exposure without using a large photomask.